WHO: Exhaust fumes more cancer causing than secondhand smoke

Exhaust fumes inhaled from diesel engines cause cancer, the World Health Organization declared Tuesday, a ruling experts said could make exhaust as important a public health threat as secondhand smoke.

“The scientific evidence was compelling and the working group’s conclusion was unanimous: Diesel engine exhaust causes lung cancer in humans,” Christopher Portier, chairman of the International Agency for Research on Cancer (IARC), the World Health Organization's cancer arm, said in a statement Tuesday.

“Given the additional health impacts from diesel particulates, exposure to this mixture of chemicals should be reduced worldwide."

It's raised the status of diesel exhaust from "probable carcinogen" to carcinogen. That means diesel exhaust joins the same category as other known hazards such as tobacco, asbestos, arsenic and ultraviolet radiation.

The new classification follows a weeklong meeting of international experts in France organized by the IARC, who analyzed published studies, evidence from animals and limited research in humans.

One of the biggest studies the group analyzed found that diesel fumes was more cancer causing than secondhand cigarette smoke, but a much smaller risk than smoking two packs a day, said Dr. Debra T. Silverman, a cancer researcher for the United States government who headed the landmark study that led to Tuesday’s decision, The New York Times reports.

That paper, published in March by the U.S. National Cancer Institute, analyzed 12,300 miners for several decades starting in 1947. Researchers found that nonsmoking miners who were heavily exposed to diesel exhaust fumes had a seven times higher risk of dying from lung cancer than nonsmokers not similarly exposed.

Health groups praise the ruling

Dr. Otis W. Brawley, the medical director of the American Cancer Society, praised the ruling telling The New York Times that his group “has for a long time had concerns about diesel.”

This recognition, coming from the world’s foremost authority on dangerous carcinogens, has been a longtime in coming, said Diane Bailey over at the Natural Resources Defense Council.

"With millions of old, dirty diesel engines in use around the world, we need governments to commit to the phase in of cleaner diesel fuels and replacement of older engines with much cleaner modern diesel technology that is widely available," she writes. "Here in the U.S. we need sustained commitment and funding for the replacement of old, polluting diesel engines."

Diesel Industry: Don't look at us

The diesel industry, as you might expect, didn't take the news too well. "Diesel exhaust is only a very small contributor to air pollution," the Diesel Technology Forum, a group representing companies including Mercedes, Ford and Chrysler, said in a statement. "In southern California, more fine particles come from brake and tire wear than from diesel engines."

For others, the 50 year study was the problem. According The Associated Press, lobbyists for the diesel industry said the study had a few cracks in it and argued that the study wasn't credible.

"It's pretty well known that if you get enough exposure to diesel, it's a carcinogen," said Ken Donaldson, a professor of respiratory toxicology at the University of Edinburgh who wasn't surprised by the upgrade in cancer status, the AP reported.

But Donaldson also said let's face it, lung cancer is a complicated disease. And despite the landmark study saying otherwise, he said that other things like smoking were far more deadly.

"For the man on the street, nothing has changed," he said. "It's a known risk but a low one for the average person, so people should go about their business as normal ... you could wear a mask if you want to, but who wants to walk around all the time with a mask on?"